Scanned retinal display with exit pupil selected based on viewer&#39;s eye position

ABSTRACT

A scanned retinal display includes an optical scanning array to generate multiple exit pupils in conjunction with an eyepiece. The multiple exit pupils expand the effective exit pupil. As a user moves their eye the eye moves from one exit pupil to another. A scanning array creates the multiple exit pupils to maintain a clear line of sight for an augmented display. Also, a viewer&#39;s eye position is tracked. To achieve a larger effective exit pupil and the pin hole effect advantage of a small exit pupil, only one exit pupil of the multiple pupils is active to enter the user&#39;s eye.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. Pat. No. 6,043,799 issued Mar. 28, 2000based on Application Ser. No. 09/027,356 filed Feb. 20, 1998 for“Virtual Retinal Display with Scanner Array for Generating Multiple ExitPupils.”

BACKGROUND OF THE INVENTION

This invention relates to retinal display devices and optical scannerdevices, and more particularly to methods for duplicating exit pupilsand for switching among exit pupils.

A virtual retinal display (VRD_(™)) device is an optical device forgenerating a virtual image to be perceived by a viewer's eye. Light isemitted from a light source, collimated through a lens, then passedthrough a scanning device. The scanning device defines a scanningpattern for the light. The scanned light converges to focus points of anintermediate image plane. As the scanning occurs the focus point movesalong the image plane (e.g., in a raster scanning pattern). The lightthen diverges beyond the plane. An eyepiece is positioned along thelight path beyond the intermediate image plane at some desired focallength. An “exit pupil” occurs shortly beyond the eyepiece in an areawhere a viewer's eye pupil is to be positioned.

A viewer looks into the eyepiece to view an image. The eyepiece receiveslight that is being deflected along a raster pattern. Light thusimpinges on the viewer's eye pupil at differing angles at differenttimes during the scanning cycle. This range of angles determines thesize of the virtual image perceived by the viewer. Modulation of thelight during the scanning cycle determines the content of the image. Fora see-through display a user sees the real world environment around theuser, plus the added image of the display projected onto the retina.

Typically, the exit pupil defined by the display device is less than 2mm in diameter and often less than 1 mm in diameter. The viewer's eyepupil varies from approximately 2 mm in diameter under bright light toapproximately 7 mm in a dark environment. Because of the small exitpupil, a first step for a viewer is to adjust eye position to find theexit pupil. The viewer's pupil needs to achieve and maintain alignmentwith the display device's exit pupil so that light from the displaydevice can enter the user's pupil and reach the viewer's retina. Whilein alignment, the light can scan directly onto the viewer's retinawithout any intermediary screens, cathode ray tubes (CRT's) or liquidcrystal display devices (LCD's). The result is an image perceived by theviewer.

A shortcoming of conventional scanned retinal displays is the difficultyof maintaining alignment between the exit pupil and the viewer's pupil.If the viewer moves, alignment may be lost. Movement is problematicbecause the viewer's eye tends to move when the viewer attempts to viewa peripheral portion of the image. Movement of the viewer's headrelative to the display or even blinking may move the eye relative tothe exit pupil. As a result, conventional exit pupils are inconvenientfor the viewer. In particular a lay consumer using a virtual retinaldisplay would find the alignment requirement difficult to maintain forlong term viewing applications, such as entertainment, or for wide fieldview images. Accordingly, there is a need for a scanned display devicehaving an exit pupil defined so as to enable easier viewing of theimage.

Within the scanned display, optical scanners typically scan light ontothe retina. In an exemplary configuration one scanner is used to providehorizontal deflection of a light beam, while another scanner is used toprovide vertical deflection of the light beam. Together the two scannersdeflect the light beam along a raster or similar pattern. Each of thescanners includes a respective mirror that deflects light along a pathdefined by the deflection angle of the mirror. At the same time that thebeam is scanned, the beam also is modulated responsive to imageinformation, such as video signals. Where the display is a colordisplay, the image information includes RGB color data that is used toseparately modulate red, green and blue components of the light beam.The three modulated components are then combined and scanned in rasterformat onto the retina to produce a color virtual image.

Scanning rate and physical deflection distance characterize the movementof the scanner's mirror. In the context of a scanned retinal display thescanning rate and deflection angles are defined to meet the limits ofthe human eye. The scanning rate determines the number of times the beamstrikes a region of the retina in a given time period. For the eye tocontinually perceive an ongoing image the light beam rescans the image,or a changing image, in periodic fashion. Analogous to refreshing apixel on a display screen, the eye's retinal receptors must receivelight from the scanning light beam periodically. The minimum refreshrate is a function of the light adaptive ability of the eye, the imageluminance, and the length of time the retinal receptors perceiveluminance after light impinges. To achieve television quality imagingthe refresh rate typically is at least 50 to 60 times per second (i.e.,≧50 Hz to 60 Hz). Further, to perceive continuous movement within animage the refresh rate typically is at least 30 Hz.

The mirror deflection angle is defined by the desired field of view andthe eyepiece magnification. The field of view is the range of angles atwhich the retina receives light. Larger fields of view correspond tolarger scan angles.

SUMMARY OF THE INVENTION

According to the invention, a scanned display includes an opticalscanning array to generate a plurality of exit pupils. As a user's eyemoves, the eye receives light from successive exit pupils. The usertherefore has more freedom of movement while viewing images from thevirtual retinal display. The device thus generates multiple exit pupilswithout placing an exit pupil expansion device at the intermediary imageplane. This method of generating multiple exit pupils leaves the line ofsight clear while expanding the effective exit pupil of the scanneddisplay. This is particularly advantageous in an augmented visiondisplay which includes a real world view and an overlaid image.

According to another method of this invention, a viewer's eye positionis tracked to determine which of the exit pupils is aligned with theeye. The determined exit pupil is enabled, while the remaining exitpupils are blocked or disabled. An advantage of this method is thatsmall exit pupils are generated instead of a single large exit pupil.The small exit pupils increase the display resolution for a person withimpaired vision through a pinhole effect to reduce optical effects ofeye aberrations. Thus, the advantages of a larger effective exit pupilare achieved by generating multiple exit pupils, while the advantages ofthe pin hole effect are achieved concurrently by enabling only the oneexit pupil which is to enter the user's eye.

These and other aspects and advantages of the invention will be betterunderstood by reference to the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a scanned retinal display according to anembodiment of this invention;

FIG. 2 is an optical schematic of the scanned retinal display accordingto an embodiment of this invention;

FIG. 3 is a diagram of light from 3 exit pupils directed toward an eye;

FIG. 4 is a perspective drawing of an exemplary scanning array for ascanning subsystem according to an embodiment of this invention;

FIG. 5 is a planar top view of the scanning array of FIG. 4;

FIG. 6 is a planar side view of the scanning array of FIG. 4;

FIG. 7 is another planar side view of the scanning array of FIG. 4; and

FIG. 8 is a diagram of an augmented scanned retinal display according toan embodiment of this invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS Overview

FIG. 1 is a block diagram of a scanned retinal display 10 according toan embodiment of this invention. The display 10 generates andmanipulates light to create color or monochrome images having narrow topanoramic fields of view and low to high resolutions. Light modulatedwith video information is scanned directly onto the retina of a viewer'seye E to produce the perception of an erect virtual image. The display10 may be small in size and suitable for hand-held operation or formounting on the viewer's head.

The display 10 includes an image data interface 11 which receives animage signal, such as an RGB signal, NTSC signal, VGA signal or otherformatted color or monochrome video or image data signal, from acomputer device, video device or other digital or analog image datasource. The image data interface generates signals for controlling alight source 12. Light generated by the display 10 is altered accordingto the image data to generate image elements (e.g., image pixels) whichform an image scanned onto the retina 13 of a viewer's eye E.

The light source 12 includes one or more point sources of light. In oneembodiment red, green, and blue light sources are included. Preferablythe emitted light is spatially coherent. Light from the light sources 12is modulated according to the input image data signal content to producelight which is input to an optics subsystem 14. The light may bemodulated by directly modulating the light source 12 or by a lightmodulator external to the light source 12.

The emitted light 36 is deflected by a scanner subsystem 16 toward aneyepiece 20 that shapes and focuses the scanned light for viewing by theeye E. The scanning subsystem includes a horizontal scanner and avertical scanner that typically deflect the light along a rasterpattern, although in an alternative embodiment another display formatsuch as vector imaging can be used. In one embodiment the scanningsubsystem 16 receives a horizontal deflection signal and a verticaldeflection signal derived from the image data interface 11. In anotherembodiment, the scanning subsystem is modulated independently of theimage signal. For example, the scanning subsystem 16 may include amechanically resonant scanner, such as that described incommonly-assigned U.S. Pat. No. 5,467,104 issued Nov. 14, 1995 for“Virtual Retinal Display”. In such embodiment, the image data interface11 buffers the image data in an intermediate memory and then forwardsthe image data to the light source 12 in response to the detectedposition of the resonant scanner.

According to an embodiment of this invention either one of thehorizontal scanner or vertical scanner 26 is formed by a scanner array24. In a preferred embodiment shown in FIG. 2 the horizontal scanner isthe scanner array and includes three scanner elements 40,42,44. Thescanner array 24 generates an array of redundant exit pupils 30, 32, 34at any given time. Although 3 exit pupils 30-32 are shown fewer or moreexit pupils are generated by an optical scanner array having fewer ormore scanners.

In one embodiment the position of the eye E is monitored by an eyetracker 22. The eye tracker receives light reflected from the eye E backthrough the eyepiece 20 and split off by a beam splitter 22. Theposition of the eye is used to identify which of the array of exitpupils 30, 32, 34 is aligned with the eye. In one embodiment only thealigned exit pupil is active—the others being blocked or blanked.

FIG. 3 shows a configuration for an augmented scanned display in whichthe viewer sees the real world with an image overlaid on all or aportion of the field of view. The eyepiece 22 is a lens which reflectslight received from the scanner subsystem 16. The scanner array depictedincludes three scanner elements 40, 42, 44. Scanner element 40 generatesexit pupil 30. Scanner element 42 generates exit pupil 32. Scannerelement 44 generates exit pupil 34.

Light Source

The light source 12 includes a single or multiple light sources. Forgenerating a monochrome image a single monochrome source typically isused. For color imaging, multiple light sources are used. Exemplarylight sources are colored lasers, laser diodes or light emitting diodes(LEDs). Although LEDs typically do not output coherent light, lenses areused in one embodiment to shrink the apparent size of the LED lightsource and achieve flatter wave fronts. In a preferred LED embodiment asingle mode monofilament optical fiber receives the LED output to definea point source which outputs light approximating coherent light.

Additional detail on these and other light source 12 embodiments arefound in U.S. Pat. No. 5,596,339 issued Jan. 21, 1997 for “VirtualRetinal Display with Fiber Optic Point Source” (Ser. No. 08/439,818,filed May 9, 1995), and incorporated herein by reference.

According to alternative embodiments, the light sources or the lightgenerated by the point sources are modulated to include red, green,and/or blue components at a given point (e.g., pixel) of a resultingimage. Respective beams of the point sources are modulated to introducecolor components at a given pixel.

Image Data Interface

An exemplary embodiment of the image data interface 11 extracts colorcomponent signals and synchronization signals from the received imagedata signal. Extracted red, green and blue components are routed torespective modulators. In response the modulators modulate light fromthe red, green and blue light sources according to the information stateof the extracted components. The image data signal interface 11 alsoextracts a horizontal synchronization component and verticalsynchronization component from the image data signal. As discussedabove, such signals can define respective frequencies for horizontalscanner and vertical scanner drive signals routed to the scanningsubsystem 16 or can be used to clock data into the intermediate memoryfor buffering.

Optics Subsystem

The optics subsystem 14 receives the light output from the light source,either directly or after passing through the scanning subsystem 16. Insome embodiments the optical subsystem collimates the light. In anotherembodiment the optics subsystem converges the light. Left undisturbedthe light converges to a focal point then diverges beyond such point. InFIG. 2 the focal point occurs between the scanning subsystem 16 andeyepiece 22. As the converging light is deflected, however, the focalpoint is deflected. The pattern of deflection defines a pattern of focalpoints. Such pattern is referred to as an intermediate image plane.

Scanning Subsystem

The scanning subsystem 16 is located after the light sources 12, eitherbefore or after the optics subsystem 14 and contains the horizontal andvertical scanners 24, 26. In one embodiment the horizontal scanner 24includes the array of scanning elements 40, 42, 44 for performinghorizontal beam deflection and the vertical scanner 26 is agalvanometer. In alternative embodiments the vertical scanner can beformed by acousto-optical deflectors, electro-optical deflectors, orrotating polygon scanners. The vertical scanner 26 receives a drivesignal having a frequency defined by the vertical synchronization signalVSYNC extracted at the image data interface 11. Preferably, thehorizontal scanner 26 receives a drive signal approximating its resonantfrequency. As will be explained below, the image data interface adjuststhe rate at which image data arrives at the respective opticalmodulators in response to the detected frequency of the scanningelements 40,42,44. Thus, the modulation rate of the light beams isdefined indirectly by the resonant frequency of the scanning elements sothat during each scan of the scanning elements 40,42, 44 one line ofimage data is output by the respective modulators.

FIG. 4 shows the scanner array 24 in an area detail with scanningelements 40, 42, 44. Each scanning element 40, 42, 44 includes a mirror56 driven by a magnetic circuit so as to oscillate at a high frequencyabout a respective axis of rotation 58. Although three scanning elementsare shown fewer or more are included in other embodiments. In oneembodiment the only moving parts are the mirrors 56 and respectivespring plates 60. The mirrors 56 are mounted to or formed by a polishedsurface of the spring plates 60. The optical scanner array 24 alsoincludes a base plate 62 that carries electromagnetic coil pairs 64 andcorresponding stator posts 66 for each of the mirrors 56. In theembodiment shown there are three pairs of coils/posts per mirror 56. Thestator coils 64 a and 64 b of each pair are wound in opposite directionsabout the respective stator posts 66 a and 66 b. The electrical coilpairs 64 are connected in series or in parallel to a drive circuit asdiscussed below.

Mounted on opposite ends of the base plate 62 are first and secondmagnets 68, 70 for each spring plate 60. The magnets 68, 70 for a givenspring plate 60 are equidistant from the stator posts 66 for such springplate 60 and corresponding mirror 56. The base 62 forms respectivebackstops 72 and seats for the magnets 68, 70.

The spring plates 60, magnets 68, 70 and the base plate 62 are tightlyclamped together by respective spring plate caps 74, 76. Each cap 74, 76is formed as a block with openings. The openings are formed so that thecaps 252, 258 can accommodate the ends 61, 63 of the spring plates 60,and the magnets 68, 70. Each cap 74, 76 is held securely to the baseplate 62 so as to clamp the spring plates 60 and magnets 68, 70 to thebase 62.

The spring plates 62 are formed of spring steel and are torsionalsprings having a spring constant determined by their lengths and widths.Ends of the spring plates rest on respective poles of the respectivemagnets 68, 70. The magnets 68, 70 are oriented such that they have likepoles adjacent the spring plates.

Each mirror 56 is mounted directly over the corresponding stator posts66 a and 66 b such that the axis of rotation 58 of the mirror isequidistant from the stator posts 66 a and 66 b. Each mirror 56 ismounted on or coated on or formed by a polished portion of thecorresponding spring plate 60. The three mirrors 56 and spring plates 60are machined to close tolerances to assure that their resonantfrequencies are substantially the same. If the resonant frequenciesdiffer slightly, the mirrors 56 and spring plates 60 may be polished orweighted to shift the resonant frequencies closer together. For finetuning the frequencies, one or more of the spring plates 60 may bestressed or compressed slightly by respective piezoelectric transducerselectromagnetic servomechanisms to shift the resonant frequency.

Magnetic circuits are formed in each scanning element 40,42,44 tooscillate the respective mirrors 56 about the axes of rotation 58 inresponse to respective alternating drive signals. For each mirror 56,one magnetic circuit extends from the top pole of the magnet 68 to thespring plate end 61, through the spring plate 60, across a gap to eachof the three stators 66 a and through the base plate 62 back to themagnet 68 through its bottom pole. Another magnetic circuit extends fromthe top pole of the other magnet 70 to the other spring plate end 63,through the spring plate 60, across a gap to the three stators 66 a andthrough the base plate 62 back to the magnet 70 through its bottom pole.Similarly, magnetic circuits are set up through the stators 66 b foreach mirror 56.

When a periodic drive signal such as a square wave is applied to theoppositely wound coils 64 a and 64 b for a given mirror 56, magneticfields are created which cause such mirror 56 to oscillate back andforth about the axis of rotation 58. More particularly, when the squarewave is high for example, the magnetic field set up by the magneticcircuits through the stators 66 a and magnets 68 and 70 cause an end ofthe mirror to be attracted to the stators 66 a. At the same time, themagnetic field created by the magnetic circuits extending through thestators 66 b and the magnets 68 and 70 cause the opposite end of themirror 56 to be repulsed by the stators 66 b. Thus, each such mirror 56is caused to rotate about the axis of rotation 56 in one direction. Whenthe square wave goes low, the magnetic field created by the stators 66 arepulse the end of the spring plate 60 whereas the stators 66 b attractthe other end of the spring plate 60 so as to cause the mirror 56 torotate about the axis 56 in the opposite direction.

In alternative embodiments, the scanning array 24 instead includesacousto-optical deflectors, electro-optical deflectors, rotatingpolygons or galvanometers to perform the horizontal deflection.

Eyepiece

The eyepiece 20 typically is a multi-element lens or lens systemreceiving the light beam(s) prior to entering the eye E. In analternative embodiment, the eyepiece 20 is a single lens. The eyepiece20 serves to relay the rays from the light beam(s) toward a viewer'seye. In particular the eyepiece 20 contributes to the location where anexit pupil of the retinal display 10 forms. The exit pupil is the imageof the scanner aperture formed by the eyepiece. The eyepiece 20 definesthe exit pupil at a known distance d from the eyepiece 20. Such locationmay be the expected location for a viewer's eye E.

In one embodiment the eyepiece 20 is an occluding element which does nottransmit light from outside the display device 10. In an alternativeembodiment, an eyepiece 20 includes a lens system that is transmissiveso as to allow a viewer to view the real world in addition to thevirtual image. In yet another embodiment the eyepiece is variablytransmissive to maintain contrast between the real world ambientlighting and the virtual image lighting. For example a photosensordetects ambient lighting. A bias voltage is generated which applies avoltage across a photochromatic material to change the transmissivenessof the eyepiece 20.

Eye Tracker

Referring to FIG. 2, a portion of the light striking the eye E isreflected back through the eyepiece 20 toward the scanning subsystem 16.Before reaching the scanning subsystem 16 light reflected back from theeye E strikes a beamsplitter 18 which directs a portion to the eyetracker 22. The eye tracker adjusts the scanning subsystem 16 to shiftthe location of the exit pupils 30, 32, 34, thereby re-aligning the oneor more exit pupils with the pupil of the eye E. An exemplary eyetracker is the Model 210 Eye Movement Monitor manufactured by AppliedScience Laboratories of Bedford, Mass. Advantageously, in thisembodiment the number of exit pupils may be small because the eyetracker 22 helps acquire the scanned beam, thereby reducing thedifficulty of eye pupil to exit pupil alignment

Method for Generating Multiple Exit Pupils

According to an embodiment of this invention, only one of the multipleexit pupils remains active at a given time. For such embodiment the eyetracker determines the position of the eye pupil and the exit pupils towhich the eye pupil is not aligned are deactivated or dimmed. In suchembodiment each of the mirrors 56 receives a separately modulated beam,rather than sharing a beam with the other mirrors 56. During theviewer's acquisition of the image, all of the beams are active. However,once the eye tracker 22 determines that the eye pupil is aligned to oneof the exit pupils 30, 32, 34 the remaining beams are dimmed or blocked.In one embodiment, the exit pupils are deactivated by controlling thedrive signals to the respective mirrors 56. With no signal applied, thedeactivated mirrors 56 return to their rest positions. In the restpositions, the mirrors 56 are angled so that they reflect light along ablocked optical path, whereby the reflected light is blocked fromreaching the viewer's eye E.

Alternatively, the respective beams may be dimmed or blocked fromreaching the respective mirrors by beam deflectors. In anotheralternative embodiment where each mirror includes an independent lightsource, the drive signal to the light source may be adjusted tocorrespond to a black image. Such an embodiment may be advantageous inapplications where the resonant frequencies of the mirrors are difficultto synchronize by compensating for differences in scanning frequenciesby adjusting the timing of data output from the buffered intermediatememory.

The benefit of activating only one exit pupil entering the eye is that asmall exit pupil is formed which enables a viewer having aberrations orother eyesight defects to see the image clearly. The small exit pupil isbeneficial to such viewer based upon what is referred to as a pinholeeffect. Specifically, rays from the small diameter exit pupil convergeupon a small portion of the retina. For a larger exit pupil theconvergence area on the retina is larger for those with poor eyesight.Thus, the image appears blurry to such persons with certain eyesightdefects. For a viewer with normal eyesight the rays converge to a pointregardless of the exit pupil size. Thus, this method provides theadvantage of multiple exit pupils which allow a viewer to see a virtualimage overlaid upon a real background in an augmented display whilemoving the eye. This method also provides the advantages of a pinholeeffect beneficial to those with certain eyesight defects.

FIG. 8 shows an optical schematic for an augmented scanned retinaldisplay according to an embodiment of this invention. The display 10′includes an image data interface 11 which receives image data from acomputer device, video device or other digital or analog image datasource. The image data interface generates signals for controlling thelight source 12. Light generated by the display 10 is altered accordingto the image data to generate image elements (e.g., image pixels) whichform an image scanned onto the retina of a viewer's eye E. The lightenters an optics subsystem 14 and a scanning subsystem 16 having anoptical scanner 24. The scanned light is then combined with the lightfrom the ambient environment by beam splitters 80, 82, then is directedtoward an eyepiece 20. As with the previously described embodiment, theoptical scanning subsystem 16 scans the light so that multiple exitpupils 30, 32, 34 occur at a known distance from the eyepiece 20 towardthe eye E. Advantageously, the beam splitters 80, 82 shift thenon-transparent parts of the display 10′ out of the viewer's line ofsight. Thus, the viewer is able to see the surrounding real worldambient environment. The viewer perceives the virtual image assuperimposed over the background light from the ambient environment.

Although preferred embodiments of the invention have been illustratedand described, various alternatives, modifications and equivalents maybe used. Therefore, the foregoing description should not be taken aslimiting the scope of the inventions which are defined by the appendedclaims.

What is claimed is:
 1. A retinal display apparatus for producing ascanned image for viewing by a viewer's eye in response to an image datasignal, comprising: a light source for generating light, wherein thelight is modulated as a function of the image data signal to defineimage content; an optical scanner array having a plurality of lightreflecting surfaces, the light reflecting surfaces moving at asubstantially common frequency with each of the other light reflectingsurfaces of the plurality of light reflecting surfaces, wherein lightoriginating from the light source impinges in parallel upon each onelight reflecting surface of the plurality of light reflecting surfaces,and wherein light is redirected by each respective one of the pluralityof light reflecting surfaces along a corresponding one of a plurality ofoptical paths; an eyepiece, positioned along the plurality of opticalpaths between the eye and the scanner array, receiving the redirectedlight from each one of the plurality of light reflecting surfaces toform a plurality of respective exit pupils through which the image isscanned, wherein there is a one to one correspondence between each oneexit pupil of the plurality of exit pupils and a corresponding oneoptical path of the plurality of optical paths and a corresponding onelight reflecting surface of the plurality of light reflecting surfaces;and an eye tracker which determines position of a viewer's eye, whereinthe image is scanned onto the viewer's eye through one exit pupil of theplurality of exit pupils, said one exit pupil selected based upon theposition of the viewer's eye determined by the eye tracker.
 2. Theapparatus of claim 1, wherein the light source generates multiple beams,each one of the multiple beams impinging on a corresponding one of theplurality of light reflecting surfaces.
 3. The apparatus of claim 1,wherein the viewer has a line of sight which is a combination of a realworld view of the viewer's ambient environment augmented with thescanned image to form an augmented view, the augmented view achieved bylocating the light source and optical scanner out of the viewer's directline of sight.
 4. A retinal display apparatus for producing a scannedimage for viewing by a viewer's eye in response to an image data signal,comprising: a plurality of light sources for generating respective lightbeams, wherein each respective light beam is modulated as a function ofthe image data signal to define image content; an optical scanner arrayhaving a plurality of light reflecting surfaces, each of the lightreflecting surfaces moving at a respective frequency, wherein the lightbeam from each respective light source impinges upon a respective one ofthe plurality of light reflecting surfaces and is redirected along arespective optical path of a plurality of optical paths, wherein eachrespective light source generates the respective light beam synchronizedto the frequency of motion of a corresponding one of the respectivelight reflecting surfaces; an eyepiece positioned along the plurality ofoptical paths between the eye and the scanner array receiving theredirected light respectively from each one of the plurality of lightreflecting surfaces to form a plurality of corresponding exit pupilsthrough which the image is scanned, wherein there is a one to onecorrespondence between each one exit pupil of the plurality of exitpupils and a corresponding one optical path of the plurality of opticalpaths and a corresponding one light reflecting surface of the pluralityof light reflecting surfaces; and an eye tracker which determinesposition of a viewer's eye, wherein the image is scanned onto theviewer's eye through one exit pupil of the plurality of exit pupils,said one exit pupil selected based upon the position of the viewer's eyedetermined by the eye tracker.
 5. The apparatus of claim 4, wherein theviewer has a line of sight which is a combination of a real world viewof the viewer's ambient environment augmented with the scanned image toform an augmented view, the augmented view achieved by locating thelight source and optical scanner out of the viewer's direct line ofsight.
 6. A method for generating an exit pupil for a retinal displaydevice, the retinal display device receiving an image data signal andscanning an image derived from the image data signal upon a viewer'seye, the method comprising the steps of: generating light modulated as afunction of the image data signal to define image content; receiving themodulated light at an optical scanner array having a plurality of lightreflecting surfaces, the light reflecting surfaces moving at asubstantially common frequency, the light impinging in parallel uponeach one light reflecting surface of the plurality of light reflectingsurfaces, the impinging light being redirected by each respective one ofthe plurality of light reflecting surfaces along a corresponding one ofa plurality of optical paths; receiving the redirected light from eachone of the plurality of light reflecting surfaces at an eyepiece;forming with the eyepiece a plurality of exit pupils from the lightreceived, respectively, from the plurality of light reflecting surfaces,wherein each one exit pupil of the plurality of exit pupils is formedfrom the light received at the eyepiece from a corresponding one lightreflecting surface of the plurality of light reflecting surfaces,wherein there is a one to one correspondence between each one exit pupilof the plurality of exit pupils and a corresponding one optical path ofthe plurality of optical paths and a corresponding one light reflectingsurface of the plurality of light reflecting surfaces; tracking eyeposition of the viewer's eye; determining, based on the tracked eyeposition, an exit pupil aligned with an entrance pupil of the viewer'seye; and scanning the modulated light onto the viewer's eye through thealigned exit pupil.
 7. The method of claim 6, wherein the viewer has aline of sight which is a combination of a real world view of theviewer's ambient environment augmented with the scanned image to form anaugmented view, the augmented view achieved by locating the opticalscanner out of the viewer's direct line of sight.